1. Field of the Invention
The present invention relates to a method and an apparatus for simply and sensitively detecting impurities, and in particular, to a method and an apparatus for carrying out impurity measurement, defect inspection, and corrosion evaluation for microstructures.
2. Background Art
In recent years, semiconductor integrated circuit devices have been configured to provide many functions, and there has been a demand for advanced integration in which a plurality of circuits are formed on one semiconductor chip. Furthermore, in order to reduce the manufacture costs of semiconductor integrated circuit devices, much effort has been made to develop a microwiring structure by reducing the widths of semiconductor elements and wires and the area of a semiconductor chip to increase the number of chips acquired per semiconductor wafer. For the improved reliability of devices such as chips or wafers including microwiring, a material needs to be developed which has few microimpurities and microdefects and which is unsusceptible to corrosion. A process technique for the material also needs to be developed. This also applies to hard disks, printed circuit boards, mounting materials, nanocomposite materials, and functional materials. The corrosion problem has been focused for, in addition to the above-described electronic components and materials, structural materials used for housings of power generation facilities and home appliances. In particular, if such a structural material is used in a high-temperature and high-humidity environment, a corrosion starting point is likely to be generated by long exposure to the high-temperature and high-humidity environment. Thus, the material is likely to be cracked or to become fragile.
Acc. Chem. Res., 23, 357 (1990) describes scanning electrochemical microscopy (SECM) which uses a probe composed of microelectrodes and in which electrodeposition of metal on specimen electrodes and etching of the surfaces of metal and semiconductor electrodes are locally carried out. Electrochemical reaction is caused on the substrate surface utilizing a local increase, at a position immediately below the probe, in the concentration of ion species generated on the probe.
Jpn. J. Appl. Phys., 32, L863 (1993) discloses local deposition, in a solution containing pyrrole, of polypyrrole on an HOPG substrate using an STM (Scanning Tunneling Microscope) probe. Specifically, the potential of a specimen substrate is set to a value obtained immediately before deposition of polypyrrole. The potential of the probe is set to a value larger than that of the specimen substrate. Then, the probe is used to scan the surface of the HOPG substrate. Thus, polypyrrole is locally deposited. The mechanism of this reaction has been discussed as follows. First, a pyrrole monomer is oxidized on the STM probe. Pyrrole is adsorbed on HOPG more easily than the probe. Hence, the subsequent polymerization reaction progresses on the HOPG.
In JP 9-143799 A, a first working electrode and a second working electrode (probe) are installed in a liquid; the first working electrode is used as a specimen serving as a site of electrochemical reaction, and the second working electrode is located locally opposite the first working electrode. The potential of each of the first and second working electrodes is set to a given value. The inter-surface distance D between the two working electrodes is set to a given value equal to or smaller than the value of thickness of an electric double layer in the liquid. Then, the potential of the second working electrode or the inter-surface distance D is varied to control the electrochemical reaction on the first working electrode. This invention is intended to control the electrochemical reaction on the specimen electrode by controlling the potentials of the two working electrodes. That is, this invention corresponds to a method for controlling dissolution (etching) and deposition reaction on the specimen surface.